AUTHOR=Alexopoulos Athanasios , Kimbaris Athanasios C. , Plessas Stavros , Mantzourani Ioanna , Voidarou Chrysa , Pagonopoulou Olga , Tsigalou Christina , Fournomiti Maria , Bontsidis Christos , Stavropoulou Elisavet , Papaemmanouil Virginia , Bezirtzoglou Eugenia 

TITLE=Combined Action of Piperitenone Epoxide and Antibiotics Against Clinical Isolates of Staphylococcus aureus and Escherichia coli

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.02607

DOI=10.3389/fmicb.2019.02607

ISSN=1664-302X

ABSTRACT=<p>The aim of this study was to determine the antimicrobial efficiency of piperitenone epoxide (PEO) – a principal component of various aromatic plants’ essential oil – in combination with various antibiotics against 28 strains of <italic>Staphylococcus aureus</italic> and 10 strains of <italic>Escherichia coli</italic> isolated from clinical samples. <italic>Mentha spicata’s</italic> essential oil, initially collected by hydrodistillation, was then subjected to flush column chromatography affording PEO of high purity. Minimum inhibitory concentrations of PEO alone and in combination with various concentrations of antibiotics were assessed using the microdilution method. The combined action was estimated calculating the fractional inhibitory concentration (FIC) index from checkerboard assays. Our results showed that the average minimum inhibitory concentration (mg/l) of PEO alone against <italic>E. coli</italic> was 512 ± 364.7 μg/ml, which was significantly higher than 172.8 ± 180.7 μg/ml observed for <italic>S. aureus</italic>. From checkerboard assays, FIC values below the 0.5 index, indicating synergy, were observed for 59% of the drugs tested. Twelve percent of FIC index values were between 0.5 and 1, indicating additive effects, while 21% were indifferent. According to our results, PEO could be a promising antimicrobial compound when combined with specific antibiotics and deserves further study.</p>